These bowls were introduced circa 1966 and are often seen with a blue inner lining, the design was drawn/trailed onto the inside of the bowl with I believe a resin resist, then sandblasted back leaving the design standing proud (and blue if cased). I dont know how long they were produced for...maybe into the early 70s...

Hi all, the pattern is on the outside, there was another one on sale at the same time as this one it had the same markings/signature a different pattern with a blue bit in the pattern, I liked that one as well, but could not afford both, i got this one as i liked it better. I had no idea of its worth and just bought it on instinct.